This invention relates to electrolytic apparatus and electrolytic method of support for lithographic printing plate electrochemically roughening the surface of aluminum web used for support for pre-sensitized plate. More specifically, this invention relates to the electrolytic apparatus and electrolytic method with a guide roller that formed with specified structure and material.
In general, aluminum web is used as support for pre-sensitized plate, and the surface of the aluminum web is roughened like sandblasted for the purpose of improving the adhesion with the sensitive layer applied to the surface, or for the purpose of maintaining the wetting water in the process of printing, and so on.
As the means of roughening the surface of the aluminum web like sandblasted, Japanese Patent KOKOKU 62-25117 discloses, for example, the electrolytic apparatus reserving electrolyte in an electrolytic bath, installing a guide roller in the electrolytic bath, and electrolyticaly processing the surface of the aluminum web while conveying the aluminum web circularly backed by the guide roller.
However, in the above-mentioned traditional electrolytic apparatus, high-temperature electrolytic process was prohibited, for the reason of remarkable degradation of rubber that covers the surface of the metal guide roller in the high-temperature electrolytic process in which printing performance would be superior, because the guide roller was formed with covering rubber and metal core in traditional electrolytic apparatus.
That is to say, it is known that although by making the pits formed with roughening by electrochemical electrolytic treatment fine, printing performance is improved and running cost is reduced dramatically, and it is necessary to increase the temperature of electrolyte of electrochemical treatment higher than 60xc2x0 C. in order to make the pits fine. However, because the duration of life of the rubber would be about 1 month in the case where the temperature of electrolyte is higher than 60xc2x0 C., the high-temperature electrolytic treatment of higher than 60xc2x0 C. was not practical.
The primary object of this invention is to solve the above-described problems, and to provide electrolytic apparatus and electrolytic method of support for lithographic printing plate where the guide roller does not deteriorate or degrade in high-temperature nitric acid electrolytic treatment.
Another object of this invention is to provide the electrolytic apparatus and electrolytic method of support for lithographic printing plate that can be used for high-temperature nitric acid electrolytic treatment for a long time.
The inventor of the present invention examined structure and material of guide roller in order to achieve above-described object.
Electrolytic apparatus of support for lithographic printing plate of this invention is the apparatus that electrolyticaly treats aluminum web in acid electrolyte wherein the guide roller for aluminum web transportation basically comprises a skeleton section, a liquid contact section, and nonwoven fabric.
By adopting such a structure, it was found that such guide roller of the treble structure does not suffer any deformation, any change in quality for a long term, and that it is not frequent to scratch the aluminum web.
Electrolytic apparatus of support for lithographic printing plate of this invention is the apparatus that electrolyticaly treats aluminum web in acid electrolyte wherein the guide roller for aluminum web transportation comprises a skeleton section formed with strong material of intensity, a liquid contact section on the surface of the skeleton section, and nonwoven fabric which is provided on the contact surface with the aluminum web.
The liquid contact section on the surface of the skeleton section is formed with fluororesin coating of 100-3000 xcexcm in thickness and the insulation resistance value of the fluororesin coatings is 105 xcexa9cm or more in volume resistivity.
The nonwoven fabric that is provided on the contact surface with the aluminum web is formed mainly with polyphenylene sulfite or fluororesin of 5-50 mm in thickness.
In addition, the nonwoven fabric is condensed in the direction of the guide roller axis, and the nonwoven fabric is treated with the surface finish up to the range of 50-95 in surface hardness.
In the electrolytic apparatus of support for lithographic printing plate of this invention, both the roller skeleton section and the fluid contact section of the guide roller shares the intensity, the acid resistance, and the insulating ability in a way that the roller skeleton section principally takes charge of intensity, and the fluid contact section takes charge of acid resistance and insulating ability. Therefore, the intensity, the acid resistance, and the insulating ability are insured completely and reduction of the weights of the material of these sections is designed. Accordingly, the intensity, the acid resistance, and the insulating ability are insured at the same time in this invention while in the prior art, it was impossible for the guide roller formed with the polyvinyl chloride or the rubber as the material to insure these performance.
Moreover, the nonwoven fabric enables to convey the aluminum web without injuring.